populating 1 textbox from a value entered in another textbox

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ASP

Ajax

I think I can ask this one simple enough, 2 text boxes, the first get's a number value, then what I need to happen is populate the second text box based on the number entered. first text box is from one table, the 2nd box is from a second table related which needs to populate that 2nd textbox depending on the value from the first box (onchange).

I can do this with drop downs, dropdown dependant, why not text boxes? the value from the first text box will only populate 1 andswer to the second, it's not like there will be a choice after the first number is entered...uugh

thanks for any thoughts here in advance.

Mac

[CP EDIT] the first text box will have a 9 digit number to add to a table, the second text box relates that number to a name so both will be inserted to a table without any misspelled names and it also verifies to the person entering that data they typed in the right 9 digit number when they see the name associated to that number is correct. if I used a drop down on the fist part, which I got working just to get a laugh, it has over 100 entries in that drop down.

I guess, if there's an easier way to have a person enter data into a textbox, after they tab or move to the next box, information appears to validate that one entry before submit, that's what really all needs to go on there...like I said before, the dropdown works, it's just that first dropdown is huge, the child dropdown will only have one choice after the first dropdown is picked. it's really for live verification of data input before submitting to a table. Easier way? I'm all ears
thanks folks
[/CP EDIT]